CVE-2026-5429 - Kiro IDE Webview Cross-Site Scripting via Workspace Color Theme

unknownCVE-2026-5429

Bulletin ID: 2026-012-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 2026/04/02 11:30 AM PDT Description: Kiro IDE is an agentic development environment that makes it easy for developers to ship real engineering work with the help of AI agents. We identified CVE-2026-5429, where unsanitized input during web page generation in the Kiro Agent webview in Kiro IDE before version 0.8.140 allows a remote unauthenticated threat actor to execute arbitrary code via a maliciously crafted color theme name when a local user opens the workspace. This issue requires the user to trust the workspace when prompted. Impacted versions: < 0.8.140 Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.

CSIRTS triage

vendor: Kiro product: Kiro IDE Cross-site scriptingOtheraffected: < 0.8.140

What: Unsanitized input during web page generation allows a remote unauthenticated threat actor to execute arbitrary code via a maliciously crafted color theme name.
Who is affected: Users of Kiro IDE versions before 0.8.140.
Urgency: Remediation is urgent due to the risk of arbitrary code execution via XSS.
Action: Upgrade to Kiro IDE version 0.8.140 or later.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: AWS Security Bulletins (INTL · vendor-psirt · site)
Severity: unknown
Published: 2026-06-05
Exploitation: Not in CISA KEV at last sync

Original advisory: https://aws.amazon.com/security/security-bulletins/rss/2026-012-aws/

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-54290.16% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 5% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-5429	coverage & exploitation status	NVD · CVE.org

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